xref: /openbmc/linux/arch/x86/kernel/head_64.S (revision 86db9f28) 
1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 *  linux/arch/x86/kernel/head_64.S -- start in 32bit and switch to 64bit
4 *
5 *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
6 *  Copyright (C) 2000 Pavel Machek <pavel@suse.cz>
7 *  Copyright (C) 2000 Karsten Keil <kkeil@suse.de>
8 *  Copyright (C) 2001,2002 Andi Kleen <ak@suse.de>
9 *  Copyright (C) 2005 Eric Biederman <ebiederm@xmission.com>
10 */
11
12
13#include <linux/linkage.h>
14#include <linux/threads.h>
15#include <linux/init.h>
16#include <asm/segment.h>
17#include <asm/pgtable.h>
18#include <asm/page.h>
19#include <asm/msr.h>
20#include <asm/cache.h>
21#include <asm/processor-flags.h>
22#include <asm/percpu.h>
23#include <asm/nops.h>
24#include "../entry/calling.h"
25#include <asm/export.h>
26#include <asm/nospec-branch.h>
27#include <asm/fixmap.h>
28
29#ifdef CONFIG_PARAVIRT_XXL
30#include <asm/asm-offsets.h>
31#include <asm/paravirt.h>
32#else
33#define INTERRUPT_RETURN iretq
34#endif
35
36/* we are not able to switch in one step to the final KERNEL ADDRESS SPACE
37 * because we need identity-mapped pages.
38 *
39 */
40
41#define l4_index(x)	(((x) >> 39) & 511)
42#define pud_index(x)	(((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
43
44L4_PAGE_OFFSET = l4_index(__PAGE_OFFSET_BASE_L4)
45L4_START_KERNEL = l4_index(__START_KERNEL_map)
46
47L3_START_KERNEL = pud_index(__START_KERNEL_map)
48
49	.text
50	__HEAD
51	.code64
52	.globl startup_64
53startup_64:
54	UNWIND_HINT_EMPTY
55	/*
56	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
57	 * and someone has loaded an identity mapped page table
58	 * for us.  These identity mapped page tables map all of the
59	 * kernel pages and possibly all of memory.
60	 *
61	 * %rsi holds a physical pointer to real_mode_data.
62	 *
63	 * We come here either directly from a 64bit bootloader, or from
64	 * arch/x86/boot/compressed/head_64.S.
65	 *
66	 * We only come here initially at boot nothing else comes here.
67	 *
68	 * Since we may be loaded at an address different from what we were
69	 * compiled to run at we first fixup the physical addresses in our page
70	 * tables and then reload them.
71	 */
72
73	/* Set up the stack for verify_cpu(), similar to initial_stack below */
74	leaq	(__end_init_task - SIZEOF_PTREGS)(%rip), %rsp
75
76	/* Sanitize CPU configuration */
77	call verify_cpu
78
79	/*
80	 * Perform pagetable fixups. Additionally, if SME is active, encrypt
81	 * the kernel and retrieve the modifier (SME encryption mask if SME
82	 * is active) to be added to the initial pgdir entry that will be
83	 * programmed into CR3.
84	 */
85	leaq	_text(%rip), %rdi
86	pushq	%rsi
87	call	__startup_64
88	popq	%rsi
89
90	/* Form the CR3 value being sure to include the CR3 modifier */
91	addq	$(early_top_pgt - __START_KERNEL_map), %rax
92	jmp 1f
93ENTRY(secondary_startup_64)
94	UNWIND_HINT_EMPTY
95	/*
96	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
97	 * and someone has loaded a mapped page table.
98	 *
99	 * %rsi holds a physical pointer to real_mode_data.
100	 *
101	 * We come here either from startup_64 (using physical addresses)
102	 * or from trampoline.S (using virtual addresses).
103	 *
104	 * Using virtual addresses from trampoline.S removes the need
105	 * to have any identity mapped pages in the kernel page table
106	 * after the boot processor executes this code.
107	 */
108
109	/* Sanitize CPU configuration */
110	call verify_cpu
111
112	/*
113	 * Retrieve the modifier (SME encryption mask if SME is active) to be
114	 * added to the initial pgdir entry that will be programmed into CR3.
115	 */
116	pushq	%rsi
117	call	__startup_secondary_64
118	popq	%rsi
119
120	/* Form the CR3 value being sure to include the CR3 modifier */
121	addq	$(init_top_pgt - __START_KERNEL_map), %rax
1221:
123
124	/* Enable PAE mode, PGE and LA57 */
125	movl	$(X86_CR4_PAE | X86_CR4_PGE), %ecx
126#ifdef CONFIG_X86_5LEVEL
127	testl	$1, __pgtable_l5_enabled(%rip)
128	jz	1f
129	orl	$X86_CR4_LA57, %ecx
1301:
131#endif
132	movq	%rcx, %cr4
133
134	/* Setup early boot stage 4-/5-level pagetables. */
135	addq	phys_base(%rip), %rax
136	movq	%rax, %cr3
137
138	/* Ensure I am executing from virtual addresses */
139	movq	$1f, %rax
140	ANNOTATE_RETPOLINE_SAFE
141	jmp	*%rax
1421:
143	UNWIND_HINT_EMPTY
144
145	/* Check if nx is implemented */
146	movl	$0x80000001, %eax
147	cpuid
148	movl	%edx,%edi
149
150	/* Setup EFER (Extended Feature Enable Register) */
151	movl	$MSR_EFER, %ecx
152	rdmsr
153	btsl	$_EFER_SCE, %eax	/* Enable System Call */
154	btl	$20,%edi		/* No Execute supported? */
155	jnc     1f
156	btsl	$_EFER_NX, %eax
157	btsq	$_PAGE_BIT_NX,early_pmd_flags(%rip)
1581:	wrmsr				/* Make changes effective */
159
160	/* Setup cr0 */
161	movl	$CR0_STATE, %eax
162	/* Make changes effective */
163	movq	%rax, %cr0
164
165	/* Setup a boot time stack */
166	movq initial_stack(%rip), %rsp
167
168	/* zero EFLAGS after setting rsp */
169	pushq $0
170	popfq
171
172	/*
173	 * We must switch to a new descriptor in kernel space for the GDT
174	 * because soon the kernel won't have access anymore to the userspace
175	 * addresses where we're currently running on. We have to do that here
176	 * because in 32bit we couldn't load a 64bit linear address.
177	 */
178	lgdt	early_gdt_descr(%rip)
179
180	/* set up data segments */
181	xorl %eax,%eax
182	movl %eax,%ds
183	movl %eax,%ss
184	movl %eax,%es
185
186	/*
187	 * We don't really need to load %fs or %gs, but load them anyway
188	 * to kill any stale realmode selectors.  This allows execution
189	 * under VT hardware.
190	 */
191	movl %eax,%fs
192	movl %eax,%gs
193
194	/* Set up %gs.
195	 *
196	 * The base of %gs always points to fixed_percpu_data. If the
197	 * stack protector canary is enabled, it is located at %gs:40.
198	 * Note that, on SMP, the boot cpu uses init data section until
199	 * the per cpu areas are set up.
200	 */
201	movl	$MSR_GS_BASE,%ecx
202	movl	initial_gs(%rip),%eax
203	movl	initial_gs+4(%rip),%edx
204	wrmsr
205
206	/* rsi is pointer to real mode structure with interesting info.
207	   pass it to C */
208	movq	%rsi, %rdi
209
210.Ljump_to_C_code:
211	/*
212	 * Jump to run C code and to be on a real kernel address.
213	 * Since we are running on identity-mapped space we have to jump
214	 * to the full 64bit address, this is only possible as indirect
215	 * jump.  In addition we need to ensure %cs is set so we make this
216	 * a far return.
217	 *
218	 * Note: do not change to far jump indirect with 64bit offset.
219	 *
220	 * AMD does not support far jump indirect with 64bit offset.
221	 * AMD64 Architecture Programmer's Manual, Volume 3: states only
222	 *	JMP FAR mem16:16 FF /5 Far jump indirect,
223	 *		with the target specified by a far pointer in memory.
224	 *	JMP FAR mem16:32 FF /5 Far jump indirect,
225	 *		with the target specified by a far pointer in memory.
226	 *
227	 * Intel64 does support 64bit offset.
228	 * Software Developer Manual Vol 2: states:
229	 *	FF /5 JMP m16:16 Jump far, absolute indirect,
230	 *		address given in m16:16
231	 *	FF /5 JMP m16:32 Jump far, absolute indirect,
232	 *		address given in m16:32.
233	 *	REX.W + FF /5 JMP m16:64 Jump far, absolute indirect,
234	 *		address given in m16:64.
235	 */
236	pushq	$.Lafter_lret	# put return address on stack for unwinder
237	xorl	%ebp, %ebp	# clear frame pointer
238	movq	initial_code(%rip), %rax
239	pushq	$__KERNEL_CS	# set correct cs
240	pushq	%rax		# target address in negative space
241	lretq
242.Lafter_lret:
243END(secondary_startup_64)
244
245#include "verify_cpu.S"
246
247#ifdef CONFIG_HOTPLUG_CPU
248/*
249 * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
250 * up already except stack. We just set up stack here. Then call
251 * start_secondary() via .Ljump_to_C_code.
252 */
253ENTRY(start_cpu0)
254	UNWIND_HINT_EMPTY
255	movq	initial_stack(%rip), %rsp
256	jmp	.Ljump_to_C_code
257END(start_cpu0)
258#endif
259
260	/* Both SMP bootup and ACPI suspend change these variables */
261	__REFDATA
262	.balign	8
263	GLOBAL(initial_code)
264	.quad	x86_64_start_kernel
265	GLOBAL(initial_gs)
266	.quad	INIT_PER_CPU_VAR(fixed_percpu_data)
267	GLOBAL(initial_stack)
268	/*
269	 * The SIZEOF_PTREGS gap is a convention which helps the in-kernel
270	 * unwinder reliably detect the end of the stack.
271	 */
272	.quad  init_thread_union + THREAD_SIZE - SIZEOF_PTREGS
273	__FINITDATA
274
275	__INIT
276ENTRY(early_idt_handler_array)
277	i = 0
278	.rept NUM_EXCEPTION_VECTORS
279	.if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
280		UNWIND_HINT_IRET_REGS
281		pushq $0	# Dummy error code, to make stack frame uniform
282	.else
283		UNWIND_HINT_IRET_REGS offset=8
284	.endif
285	pushq $i		# 72(%rsp) Vector number
286	jmp early_idt_handler_common
287	UNWIND_HINT_IRET_REGS
288	i = i + 1
289	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
290	.endr
291	UNWIND_HINT_IRET_REGS offset=16
292END(early_idt_handler_array)
293
294early_idt_handler_common:
295	/*
296	 * The stack is the hardware frame, an error code or zero, and the
297	 * vector number.
298	 */
299	cld
300
301	incl early_recursion_flag(%rip)
302
303	/* The vector number is currently in the pt_regs->di slot. */
304	pushq %rsi				/* pt_regs->si */
305	movq 8(%rsp), %rsi			/* RSI = vector number */
306	movq %rdi, 8(%rsp)			/* pt_regs->di = RDI */
307	pushq %rdx				/* pt_regs->dx */
308	pushq %rcx				/* pt_regs->cx */
309	pushq %rax				/* pt_regs->ax */
310	pushq %r8				/* pt_regs->r8 */
311	pushq %r9				/* pt_regs->r9 */
312	pushq %r10				/* pt_regs->r10 */
313	pushq %r11				/* pt_regs->r11 */
314	pushq %rbx				/* pt_regs->bx */
315	pushq %rbp				/* pt_regs->bp */
316	pushq %r12				/* pt_regs->r12 */
317	pushq %r13				/* pt_regs->r13 */
318	pushq %r14				/* pt_regs->r14 */
319	pushq %r15				/* pt_regs->r15 */
320	UNWIND_HINT_REGS
321
322	cmpq $14,%rsi		/* Page fault? */
323	jnz 10f
324	GET_CR2_INTO(%rdi)	/* can clobber %rax if pv */
325	call early_make_pgtable
326	andl %eax,%eax
327	jz 20f			/* All good */
328
32910:
330	movq %rsp,%rdi		/* RDI = pt_regs; RSI is already trapnr */
331	call early_fixup_exception
332
33320:
334	decl early_recursion_flag(%rip)
335	jmp restore_regs_and_return_to_kernel
336END(early_idt_handler_common)
337
338	__INITDATA
339
340	.balign 4
341GLOBAL(early_recursion_flag)
342	.long 0
343
344#define NEXT_PAGE(name) \
345	.balign	PAGE_SIZE; \
346GLOBAL(name)
347
348#ifdef CONFIG_PAGE_TABLE_ISOLATION
349/*
350 * Each PGD needs to be 8k long and 8k aligned.  We do not
351 * ever go out to userspace with these, so we do not
352 * strictly *need* the second page, but this allows us to
353 * have a single set_pgd() implementation that does not
354 * need to worry about whether it has 4k or 8k to work
355 * with.
356 *
357 * This ensures PGDs are 8k long:
358 */
359#define PTI_USER_PGD_FILL	512
360/* This ensures they are 8k-aligned: */
361#define NEXT_PGD_PAGE(name) \
362	.balign 2 * PAGE_SIZE; \
363GLOBAL(name)
364#else
365#define NEXT_PGD_PAGE(name) NEXT_PAGE(name)
366#define PTI_USER_PGD_FILL	0
367#endif
368
369/* Automate the creation of 1 to 1 mapping pmd entries */
370#define PMDS(START, PERM, COUNT)			\
371	i = 0 ;						\
372	.rept (COUNT) ;					\
373	.quad	(START) + (i << PMD_SHIFT) + (PERM) ;	\
374	i = i + 1 ;					\
375	.endr
376
377	__INITDATA
378NEXT_PGD_PAGE(early_top_pgt)
379	.fill	512,8,0
380	.fill	PTI_USER_PGD_FILL,8,0
381
382NEXT_PAGE(early_dynamic_pgts)
383	.fill	512*EARLY_DYNAMIC_PAGE_TABLES,8,0
384
385	.data
386
387#if defined(CONFIG_XEN_PV) || defined(CONFIG_PVH)
388NEXT_PGD_PAGE(init_top_pgt)
389	.quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
390	.org    init_top_pgt + L4_PAGE_OFFSET*8, 0
391	.quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
392	.org    init_top_pgt + L4_START_KERNEL*8, 0
393	/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
394	.quad   level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
395	.fill	PTI_USER_PGD_FILL,8,0
396
397NEXT_PAGE(level3_ident_pgt)
398	.quad	level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
399	.fill	511, 8, 0
400NEXT_PAGE(level2_ident_pgt)
401	/*
402	 * Since I easily can, map the first 1G.
403	 * Don't set NX because code runs from these pages.
404	 *
405	 * Note: This sets _PAGE_GLOBAL despite whether
406	 * the CPU supports it or it is enabled.  But,
407	 * the CPU should ignore the bit.
408	 */
409	PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
410#else
411NEXT_PGD_PAGE(init_top_pgt)
412	.fill	512,8,0
413	.fill	PTI_USER_PGD_FILL,8,0
414#endif
415
416#ifdef CONFIG_X86_5LEVEL
417NEXT_PAGE(level4_kernel_pgt)
418	.fill	511,8,0
419	.quad	level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
420#endif
421
422NEXT_PAGE(level3_kernel_pgt)
423	.fill	L3_START_KERNEL,8,0
424	/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
425	.quad	level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
426	.quad	level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
427
428NEXT_PAGE(level2_kernel_pgt)
429	/*
430	 * 512 MB kernel mapping. We spend a full page on this pagetable
431	 * anyway.
432	 *
433	 * The kernel code+data+bss must not be bigger than that.
434	 *
435	 * (NOTE: at +512MB starts the module area, see MODULES_VADDR.
436	 *  If you want to increase this then increase MODULES_VADDR
437	 *  too.)
438	 *
439	 *  This table is eventually used by the kernel during normal
440	 *  runtime.  Care must be taken to clear out undesired bits
441	 *  later, like _PAGE_RW or _PAGE_GLOBAL in some cases.
442	 */
443	PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
444		KERNEL_IMAGE_SIZE/PMD_SIZE)
445
446NEXT_PAGE(level2_fixmap_pgt)
447	.fill	(512 - 4 - FIXMAP_PMD_NUM),8,0
448	pgtno = 0
449	.rept (FIXMAP_PMD_NUM)
450	.quad level1_fixmap_pgt + (pgtno << PAGE_SHIFT) - __START_KERNEL_map \
451		+ _PAGE_TABLE_NOENC;
452	pgtno = pgtno + 1
453	.endr
454	/* 6 MB reserved space + a 2MB hole */
455	.fill	4,8,0
456
457NEXT_PAGE(level1_fixmap_pgt)
458	.rept (FIXMAP_PMD_NUM)
459	.fill	512,8,0
460	.endr
461
462#undef PMDS
463
464	.data
465	.align 16
466	.globl early_gdt_descr
467early_gdt_descr:
468	.word	GDT_ENTRIES*8-1
469early_gdt_descr_base:
470	.quad	INIT_PER_CPU_VAR(gdt_page)
471
472ENTRY(phys_base)
473	/* This must match the first entry in level2_kernel_pgt */
474	.quad   0x0000000000000000
475EXPORT_SYMBOL(phys_base)
476
477#include "../../x86/xen/xen-head.S"
478
479	__PAGE_ALIGNED_BSS
480NEXT_PAGE(empty_zero_page)
481	.skip PAGE_SIZE
482EXPORT_SYMBOL(empty_zero_page)
483
484